<p>Domestication of warm-season forage grasses has been slow due to breeding challenges from complex ploidy systems and apomixis, as well as for the lack of genetic and genomic tools to assist breeding. Dallisgrass (<i>Paspalum dilatatum</i> Poir.) is a forage grass well-suited for warm-temperate climates. This apomictic pentaploid species belongs to the Dilatata species complex, along with allotetraploid autogamous sexual species. The phenotypic variability resulting from interspecific hybridization between these sexual species is understudied. Here, we examined the phenotypic variability of 17 quantitative traits within a RIL mapping population obtained after selfing progenies from a single cross between two sexual Dilatata species: <i>P. flavescens</i> and <i>P. plurinerve</i>. The variability was broader than that found in natural variation. Transgressive segregation was detected, and a fraction of the RILs showed phenotypic combinations different from parental lines. Additionally, we built a reliable high-density genetic map for the Dilatata species complex using 1,539 robust SNP markers, with similar quality to maps constructed for other warm-season grasses. To test the map usefulness and resolution and to gain initial insights into quantitative trait genetic architecture in these species, we localized robust QTLs using the phenotypic data for the measured traits. Correlations between traits were rare, and distances higher than 50&#xa0;cM were registered between most QTLs, indicating independent segregation of traits and QTLs. The results demonstrate the potential of interspecific hybridizations between sexual Dilatata species for forage breeding and genetic and heritability analyses.</p>